QuantiFERON-TB Gold Validation at the San Diego County Public Health Laboratory Aline Grigorian, PhD San Diego County Public Health Laboratory August 13, 2008
SDPHL Serology QuantiFERON-TB (QFT) Testing: Over 2000 tests/year Specimens received from Refugee Program, TB clinic, various hospitals Receive specimens before incubation Test performed 3-43 4 days/week Funded through TB Control Charge $69.27/test (Medi( Medi-Cal) Costs $48.00/test
QFT-GIT QFT-G
QuantiFERON-TB Validation Chronology 2005 January-March: Groundwork for QuantiFERON-TB Gold April: Manual testing validation studies begun 40 specimens tested Lack of consistent results Problems identified, corrective actions taken 2006 February: Validation of 4-pt curve April: Reviewed results with TB Clinic physicians Purchase NexGen with TB grant ($60,000) September: Validation on NexGen Four completed 18 specimens tested 2008 April: In-Tube validation completed 25 specimens tested
Manual QFT-G G Validation Groundwork 2005 January: Communication with Cellestis on validation protocol Coordination with TB Clinic on volunteers to be tested February: Ordered vacutainers, recruited volunteers Requested two QFT-G kits for validation studies April: Purchased kits (1 free, TB Clinic purchased 2nd) Cost $600/kit (2 plates, 20 specimens/plate) Training by Cellestis tech rep. (Brenda Robles) Began testing 40 specimens, tested in duplicate by two microbiologists May - Oct: Continued validation studies, but not all ELISA runs successful
QuantiFERON-TB Gold QC Standards For the ELISA run to be valid: Correlation coefficient (r) for mean OD of standards >0.98 Standard dilutions 1 to 5 within 15% of mean OD (CV <15%) Replicate ODs of standard dilutions 6 & 7 within 0.40 of mean Mean OD for standard dilution 1 >1.200 Mean OD for zero standard (green diluent) < 0.15
Manual QFT-G G Validation QFT-G Validation Summary - 2005 Run Date 4/28/2005 5/11/2005 7/15/2005 7/20/2005 9/22/2005 9/28/2005 10/3/2005 10/20/2005 Results CC too low* Stds #2 & #3 failed, CC too low Pass! Pass! Pass!, Std #5 failed Std #5 failed, CC too low CC too low Pass! *Cellestis Tech Specialist ran assay side-by-side with PH Micro CC - Correlation coefficient
Manual QFT-G G Validation QFT-G Validation Problems and Solutions Problem Defective lot of kit Defective 8 channel pipette Solutions Replaced 29 kits Failure to use shaker to mix plate Use shaker after both steps Standards out of range Inadequate plate washer Standards periodically out of range Replace pipette Use dedicated pipettes Use double volumes to prepare dilutions (SFPHL method) Biotek ELx50 washer Use 4 point curve (vs. 8 point) Use automated instrument (NexGen)
Manual QFT-G G Validation Summary of Results from 40 Patients Patient Test Results PPD Results QFT-G Results No. of Patients + + 7 + - 7 + + and - 3 - - 18 - + and - 1 - - and Comments Most received BCG vaccine 1 High background indeterminate Borderline Indeterminate 1 Low mitogen response Borderline + 1 Borderline - 1 + BCG vaccine = + PPD skin test + BCG vaccine = - QFT results
QFT-G G Validation on NexGen unit April 2006: NexGen Four unit purchased using TB grant money September 2006: 18 specimens tested in duplicate by two microbiologists All runs passed first time using 8-pt curve Different QFT-G kit lot# used Began testing patient specimens
Public Health Laboratory County of San Diego Dept. of Health Services 3851 Rosecrans St. San Diego, CA 92110 (619) 692-8500 fax: (619) 692-8558 ** Information required in order to test specimens. C. Peter, Ph.D., Chief QUANTIFERON REQUEST FORM **Patient Name (Last, First, Middle Initial) Clinical Information: TB Diagnosis Contact to TB Case **Address Other **City, State, Zip Code **Telephone **Date of birth **Sex: M F **Specimen Collected: Whole Blood with heparin anticoagulant. Submit within 12 hours of collection. **Submitter name, address and phone #: Date: Time: A.M,/P.M. Collected by: Ethnicity: Race: (Circle one) 1. White 1. Latino 2. European 2. African-American 3. African 3. Asian/Pacific Islander 4. Middle Eastern 4. American Indian 5. Other Insurance Provider:: MediCal #: Other: FOR LABORATORY USE ONLY Results: Interpretation: Negative IU/ml M. tuberculosis infection unlikely but cannot be excluded, especially when illness is consistent with TB disease and likelihood of progression to TB disease is increased. Positive IU/ml M. tuberculosis infection likely Indeterminate QFT-G results cannot be interpreted as a result of low mitogen response Both qualitative result and quantitative values are reported Indeterminate QFT-G results cannot be interpreted as a result of high background response
In-Tube Method Validation on NexGen Unit April 2008: 25 specimens tested in duplicate by two microbiologists All runs passed using 8-pt curve All results agreed between operators Four results disagreed between Manual NexGen run and In-Tube run
QFT-G G In-Tube Validation Summary of Results from 25 Patients Patient Test Results Manual No. of In-Tube NexGen Patients + + 6 - - 15 - + 2 - indeterminate 2 Comments 3rd Ag present (more sensitive) Low Mitogen response (inadequate tube shaking) Adequate shaking of the In-Tube is very important for this assay!
Summary Tested specimens from subjects with known PPD results All were tested using duplicate specimens (2 tubes drawn same day) Two different microbiologists tested all specimens in duplicate Manual QFT-G validation problems probably due to bad kit lot NexGen validation passed easily using different kit lot In-Tube method validation passed easily Adequate shaking very important for In-Tube assay
QuantiFERON-TB Technical Experts Jill Giesick Supervising Public Health Microbiologist jill.giesick@sdcounty.ca.gov Graciela Zuniga Cell Culture Senior Public Health Microbiologist graciela.zuniga@sdcounty.ca.gov Thelma DeGuzman EIA Senior Public Health Microbiologist thelma.deguzman@sdcounty.ca.gov Phone: (619) 692-8500